A transformer for vehicles is mounted, for example, under the floor of a vehicle. For railway vehicles such as those on local lines, running wind self-cooling-type transformers that use running wind created by running of vehicles are sometimes used in view of maintenance savings and energy savings, instead of forced-air cooling-type transformers that use fans to cool the transformers for vehicles. However, running wind self-cooling-type transformers have a problem in that the cooling performance, i.e., the amount of heat exchange, is lower than that of forced-air cooling-type transformers.
One example of a running wind self-cooling-type transformer is disclosed in Japanese Utility Model Laying-Open No. 56-94023 (PTL 1). That is, the winding of the transformer is cooled by circulating an oil using an oil pump. The oil is then cooled by a radiator pipe that is attached outside the transformer, utilizing running wind during running of a vehicle.
One example of an air-cooling structure is also disclosed in Japanese Patent Laying-Open No. 7-198279 (PTL 2). That is, the direction of a flat surface of a heat-receiving portion of a heat pipe differs by substantially 90° from that of a flat surface of a radiator portion of the heat pipe. This configuration is useful when air is desirably fed to the radiator portion of an assembled radiator in a direction orthogonal to a heat-receiving plate.